Hunt and lag preventing means



May i5, 19346 VB. A. wn-rKulg-lNs HUNT AND LAGr PREVENTING MEANS l FiledFeb.

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Patented May 15, 1934 UNITED STATES HUNT AND LAG PREVENTING MEANS BrunoA. Wittkuhns, Summit, N. J., assignor to Sperry Gyroscope Company, Inc.,Brooklyn, .N. Y., a corporation'oi.' New York Application February 7,1933, Serial No. 655,544

4 Claims.

- This invention relates to devices for transmitting the major rotarymovements of a shaft subject to hunting or rapid oscillations ofrelatively small amplitude without introducing any lag in 5. thernajor'transmitted movements. Thus in the gyroscopic compass art thefollow-up element on the .compass continually hunts or oscllates througha small angle (on .the order of va 'degree or two) and it is'desired totransmit the major vturning movements of this element withouttransmitting the hunt so that the repeater Compasses only show theaverage position of the compass. The hunt is especially objectionablewhere the compass readings are-magnified by coarse and 1.5 fine repeatercompasses. v,lin the past this has been accomplished by a lost motiondevice which, although moderately successful in eliminating the hunt,introduces a lag when the ship, is turning so that Athe transmittedreading is in error during that period. By my invention I have succeededin eliminatingthe hunt without introducing lag; j

Referring to the drawing illustrating several forms the invention mayassume:

Fig. 1 shows my invention as applied to agyro compass. v

Fig. 2 illustrates a simplified formv of the invention for use as atransmitting device between any driving and driven shaft.

Fig. 3 are two diagrams showing how lag is introduced by an ordinarylost motion device.

'I'he reason why lagv is introduced by a lost motion device may beappreciated by reference to Fig. 3 in which a pin P is mounted on thedriv- 3 ing or actuating oscillatory member and the driven member isshown as a plate L having a slot S therein of the length equal to orslightly greater than the normal oscillatory movements of the pin. Aslong as the pin is merely oscillating, therefore, the plate L willoccupy a central position with the index I opposite the alverageposition of the pin. Now suppose that the pin P is given a translatorymotion to the right superimposed on its oscillatory motion and of 'aboutthe same rate. The pin then will move in that direction in a series ofjumps but the average position of the plate L will no longer becentralizedwith respect to the pin but will lag behind the same adistance ,.3 approximately equal to one half of the length of the slot Sas long as the -pin is so translating. As soon, however, as thistranslatory motion stops, the position of the plate will again becentralized. Therefore, the lag is only present during translation ofthe plate or, in other words,

.ing shaft 1.

in. a gyro compassthe lag in the transmission system will only bepresent during turning of the ship.

The elements of my invention are shown in Fig. 2 in which the drivingoscillatory shaft is shown at 1 and the driven shaft at 2. Between thetwo shafts is placed a suitable form of differential gearing 3, saidgearing in Fig. 2 being shown as of the bevel gear type. The planetaryarm 4 of said gear train is connected to and turned from the shaft 1.Another arm 5 of said trainv is connected to one portion 6 of a lostmotion device 12 connecting the same to said driv- Said device is shownas comprising a. pair of cones 7 mounted on a collar 8 pinned to shaft 1and partially entering cone-shaped recesses 8' in member 6, therebyproviding a lost may be adjusted in amount by raising or lowering thecollar 8 on shaft 81. A light friction 75 brake 9 is yieldingly heldagainst the periphery lof 'member 6 by spring 10 to hold this arm of thedifferential, unless positively turned. The third or driven arm 11 ofsaid train drives the driven shaft 2 through a similar lost motionconnection, said connection being shown in the form of a pair of cones41 on member 11 which partially entercone-shaped recesses 42 in a collar13 on shaft 2, said collar likewise being provided with a.spring-pressed friction brake 14.

To understand the theory of operation, let us suppose that the lostmotion or play in the two devices is equal and that the amount of playin the lower lost motion device 12 is about twice that of Ithe normalextent of oscillation of the cones 7. As. the shaft 1 oscillates throughthis angle, the part 6 will not be moved and since it is held by a brake9 the turning of the planetary arm -through the same angle will rotatethe arm 1l through duble that angle. Therefore, if -the same amountofplay ls allowed in the device 40 as in 12, the pins 41 will beoscillated to just touch the walls of the recesses during the normalhunting action but not to move the same. Now suppose that shaft 1 isturned in one direction through sufficient distance to contact cones '7with depressions 8 but without moving the same. This motion willobviously turn the member 11- through twice this distance which,therefore, moves the shaft 2 through an angle equal to the movement ofthe cones to one side of central, or in other words, equal to the lostmotion on one side, thereby compensating at once for the entire lag.Assuming then the shaft 1 to keep turning in that direction, a furthermovement of the `nection during such translatory motion. It is obviousthat by varying the amounts of lost motion between the cones andrecesses or by altering the differential gear ratios that a greater orfless advance of the shaft 2 may be obtained for compensating for lostmotion in other parts of the transmission system, or for varyingrelative speeds of hunting and major rotation.

Fig. 1 illustrates how my invention may be ap `plied to a gyro compassor similar device between the hunting follow-up element and theelectrical transmitter which transmits the position of the compass tothe repeater compasses. The sensitive element of the compass is shown at20, the follow-up element 21 being actuated therefrom by means such asthe follow-up contacts 22-23 which actuate the azimuth motor 24 to turnthe large gear 25 on the follow-up element. The usual compass card 26may be mounted on the follow-up element and thereis also shown a gear 27thereon for turning theA transmitter 28. Between said gear andtransmitter, I interpose my lost motion devices. As shown, the drivingshaft 1', in this instance, is turned through step-up gearing29, 30 fromthe gear 27, the gear 30 meshing with a pinion 31 which is secured toshaft 1' and which carries the lost motion cones 7'. Pinion 31 is shownas secured to a sleeve 33 which is slidably but non-rotatably mounted onshaft 1'. For adjusting said sleeve to vary the amount of lost motion, Ihave shown a nut 32 threaded on the lower end of the shaft 1.' andnormally locked in place by the lock nut 34. Obviously, by loosening thelock nut and turning the nut the sleeve may be moved up and down on theshaft 1 to raise and lower the cones to vary the lost motion. Said conesengage conical openings 8 in the member 6' which may also be providedwith a brake 9'. f

As before, the shaft l turns the planetary or differential arm 4' of thedifferential gear train 3', the train in this instance being shown as ofthe spur gear type. The lower arm of said train comprises a pinion 5'which is secured to the member 6', while the upper or driven member 11'is formed by the spur pinion 35 to which is secured a cup-like annulargear 37 meshing with gear 38, which may be axially adjustablby nut 44 asin the case of pinion 31. Gear 33 carries the cones 41' of the secondlost motion device 40', the apertured disc 13' in this instance beingsecured directly to the drivenshaft 2' of the transmitter 28, -the brakebeing shown at 47. A

repeater card 48 is shown mounted on the shaft of the transmitter whichis read in connection with the index 49. In this case the repeater cardis of the fine variety, that is, for one revolution of the compass therepeater card rotates a number of revolutions, say 36, so as to givemagnified compass readings. With such fine reading compass cards, it ishighly important that all lost motion and lag be eliminated since thereadings are magnified 36 to 1 on the repeater card.

In accordance with the provisions of the patent statutes, I have hereindescribed the principle and operation of my invention, together with theapparatus which I now consider to represent the best embodiment thereof,but I desire to have it understood that the apparatus shown is onlyillustrative and that the invention can be carried out by other means.Also, while it is de- -l signed to use the various features and elementsin the combination and relationsdescribed, some of these may be alteredand others omitted without interfering with the more general resultsoutlined, and the invention extends to such use.

Having described my invention, what I claim and desire to secure byLetters Patent is:

1. In a lost motion device for eliminating hunt i without lag comprisinga driving hunting shaft, a driven non-hunting Shaft, a pair of lostmotion devices between said shafts, each device having a driving anddriven part and a differential gearing between said devices, one arm ofwhich is driven by said driving shaft, another arm by the driven part ofthe first device, and a third arm driving the driving part of the seconddevice, the driven part thereof driving said driven shaft.

2. A lost motion device as claimed in claim 1 for driving shafts subjectto 'an oscillation of limited extent in which the driving shaft turnsthe planetary arm of said differential gear train and in which the lostmotion in the first device is double the limited extent of oscillationof the driving shaft.

3. In a lost motion device for gyro Compasses -and the like, thecombination with the follow-up hunting element and a high speedtransmitter, of step-up gearing between the same, a pair of lost 1motiondevices in said gearing connected in said transmitter being driven fromsaid lastnamed device. 4. In a lost motion device for gyro Compasses andthe like, the combination with the follow-up hunting element and a highspeed transmitten.

BRUNO A. WII'I'KUHNS.

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